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Bigger challenge than PRRS

​By Greg Cima

Posted April 16, 2014

Porcine epidemic diarrhea is the biggest challenge Dr. Luc Dufresne has faced in 25 years in practice.

Dr. Dufresne, senior director of health assurance for Seaboard Foods, said challenges associated with PED outbreaks over the past year surpass even the challenges of porcine reproductive and respiratory syndrome, a viral disease that has caused deadly outbreaks and billions of dollars of damage since the causative virus emerged in the U.S. in the late 1980s.

The PED virus entered the U.S. in spring 2013, and at least two strains had been found in herds in 27 states by late March 2014. Outbreaks with the first strain discovered have been particularly deadly for the youngest pigs, killing nearly all neonatal pigs in many herds.

In March, Dr. Dufresne told fellow swine veterinarians that Seaboard Farms had some of the nation’s first outbreaks of PED during 2013, and 36 of the company’s 47 sow farms have had outbreaks. His presentation during the annual meeting of the American Association of Swine Veterinarians detailed the effects of the virus, which requires low doses for infection, is easily carried on people and vehicles, is difficult to remove from trucks through washing, and carries a risk that some animals will chronically shed the virus.

Dr. Robert Morrison, a professor of veterinary population medicine at the University of Minnesota, said environmental sampling also showed that the virus is present in a variety of locations on farms, including on doorknobs, in medicine rooms, and in areas where workers wash their boots. The likelihood a farm will have PED virus infections increases with factors such as the proximity of other farms, the frequency of rendering service visits, and the presence of wildlife such as rodents, feral hogs, and birds, he said.

In written proceedings submitted for the meeting, Dr. Morrison and Dr. Dane Goede, a graduate student at the University of Minnesota, wrote that sow herds “are becoming infected at a disturbing rate despite best attempts at biosecurity.”

The PED virus seems to be transmitted more easily than the PRRS virus, it is more environmentally stable, and sows have lower immunity to it, they wrote. Rigorous biological containment and sanitation are the only hope of preventing a larger outbreak when sows and litters have clinical signs.

Dr. John Clifford, chief veterinary officer for the Department of Agriculture, said the Animal and Plant Health Inspection Service is developing its Comprehensive and Integrated Swine Surveillance Program to provide a federal structure for reporting the presence of livestock diseases of zoonotic or economic concern, and he needs swine veterinarians’ support. APHIS has to have agreements with state governments and industry so that farms can report where a disease is present and the agency can protect the confidentiality of those providing reports.

“If it takes us one to two weeks to identify a new emerging disease like PED—the way we move livestock, it’ll already be in multiple states,” Dr. Clifford said. “Just think for a moment how much loss we have with PED and think about foot-and-mouth disease, classical swine fever, and African swine fever—those diseases that we all recognize as foreign animal diseases.”

Dr. Jerome O. Geiger, who works in the China operations of pig genetics company PIC, said it is veterinarians’ job to keep foreign diseases out of U.S. herds, protecting animals, clients, and the pork industry. But they can lose their global perspective when focusing on immediate issues such as PRRS, mycoplasmal pneumonia, antimicrobial resistance, and client education. Complacency about foreign diseases is understandable but not forgivable, he said.

Dr. Rodney “Butch” Baker, senior clinician for veterinary diagnostic and production animal medicine at Iowa State University, expects swine veterinarians will have a better understanding of, and control over, the spread of PED by the time of the next AASV annual meeting. Better vaccines and management as well as records of interventions and outcomes will help control the disease.

He noted that swine veterinarians have eliminated and conquered other diseases including pseudorabies and hog cholera. Those who started practice after those diseases were eliminated and want to build a legacy need to solve the PED problem, he said.